Various lubricants and lubricating agents have been used in drilling applications and in aqueous based drilling fluids. Lubricants such as surfactants, solid materials like glass beads, graphite, hydrocarbons like polyalphaolefins, synthetic and natural oils like glycols, fatty acid esters have all been reported in the literature as being useful in aqueous based drilling fluids. A good number of these materials are not soluble or compatible with aqueous based drilling fluids. Most of these lubricants, whether soluble or insoluble, require significant concentration to perform as lubricants.
For example it is reported that glycol and glycol ether products, more particularly the reaction product between 2-ethylhexanol and the epoxide of 1-hexadecene may be used as lubricants in aqueous drilling fluids. These products are reported to enhance the lubricity of water-based drilling fluids. Another reported lubricant for aqueous based fluids including glycol and glycol ether products, particularly the reaction product between 2-ethylhexanol and the epoxide of 1-hexadecene. These products are reported to enhance the lubricity of water-based drilling fluids. The literature also describes a lubricant system composed of a surfactant (preferably aluminum stearate), a viscosifier (oil-compatible bentonite or polyacrylamide), a filming amine, an activator (petroleum solvent, coconut oil, terpene, xylene, mineral oil, turpentine, d-limonene or mixtures thereof), and a diluent (diesel fuel, fuel oil, gasoline, naphtha, kerosene, or jet fuel). When the lubricant formulation is dispersed in the drilling fluid, the filming amine coats the metal; and friction associated with the drilling operation causes formation of a lubricious emulsion. A drilling fluid additive utilizing a monocyclic terpene (e.g., d-limonene) and an oil, such as mineral oil or vegetable oil is also reported in the literature. The additive is mixed into a water-based drilling fluid in the range of 1–8% by volume and is reported to provide improved rate of penetration, high lubricity and low toxicity.
One of skill in the art should appreciate that clear brines are often used in the drilling of subterranean wells during the penetration of the target formation and are often called completion fluids. Brine based drilling muds are also well known to one of skill in the art of drilling. Unfortunately, many if not all of the known lubricants useful in aqueous based drilling fluids are not compatible with clear brines or drilling muds that have brine as a major component. Thus there remains an unmet need for a lubricant for brine-based drilling fluids especially clear brines.